The present disclosure relates to a planetary transmission and, in particular, to a planetary transmission in which there is a reduction in friction at an axial abutment of the planet spider thereof and/or of the sun wheel shaft thereof on the cover of the transmission.
Planetary transmissions are known from DE 60 2005 005 448 T2, for example. Here, a sun wheel on a sun wheel shaft and a planet spider having planet wheels are arranged in an annulus.
Planetary transmissions are used as travel transmissions for frequent and infrequent travelers, for example. In such planetary transmissions, there is either abutment of the sun wheel with respect to the sun wheel shaft, and/or of the sun wheel shaft with respect to the cover, which is arranged on the annulus, and/or of a planet spider with respect to the cover.
In this case, there is axial guidance of the planet spider and/or of the sun wheel shaft. One particularly desirable characteristic here is reduction in friction at the axial abutment of the planet spider and/or of the sun wheel shaft on the cover of the planetary transmission. As a solution for this, consideration has been given to providing the sun wheel shaft with a cylindrical roller or sleeve. Moreover, a friction-reducing element in the cover of the transmission has been considered. As another solution, the end face of the planet spider journal has been made convex.
However, the disadvantage with such solutions is that, in general, either the planet spider journal or the mating running surface in the cover has to be hardened, e.g. nitrided. Such nitriding is very involved in terms of production technology and is very expensive, especially in the case of forged blanks, as represented by the planet wheel journal, sun wheel shaft etc.
Another disadvantage is that there is no freedom in the combination of materials in the friction partners, namely the sun wheel/sun wheel shaft or planet spider journal/cover or sun wheel shaft/cover. As a result, there may be high wear, depending on the friction partners.